MCU

cam

ESP32-CAM OV2460

links

Lightweight C compilers http://fun4diy.com/

STM8

compilers comparation http://www.colecovision.eu/stm8/compilers.shtml

startup

1. Power requirements: 3.3-5V
2. Reset circuit (100nF cap)
3. Select clock source (ext.crystal/HSI)
4. Choose halt modes for
   1. flash
   2. HSI, HSE
5. use timer or AWU for wake-up if no ext.ints
6. calibrate LSI osc.
7. configure GPIO
8. use watchdog

AWU

• on int disable AWU (or new int will be generated instantly)
• before re-enable re-load counter

UART

- word length: UART_CR1.M
- stop bits: UART_CR3
- baud rate: UART_BRR2 then UART_BRR1
- en transmitter: UART_CR2.TEN
- send data: UART_DR and wait until TC goes 1

TXE: set at end of transmission (and if TIEN then int is generated) - can send more

 wait for TXE before write DR

TC: transmission complete (and if TCIEN then int is generated) - may disable transmitter

SBK bit: send break character (do not set again before prv break is sent)

UART_CR1.R8: MSB for received 9-bit words

NF: set when start bit has spurious '1's

- en receiver: UART_CR2.REN

clear REN to abort receive immediately

RXNE: set when data moved to RDR (and intr if RIEN set)

if char is received without RXNE reset then overrun error raised

break char: received as framing error

idle char: intr if ILIEN set

- UART_CR1.PCEN : one bit of total length will be used for parity
- UART_CR1.PS : even/odd parity

- UART_CR1.RWU: mute mode. WAKE = 0: until idle, WAKE = 1: listen for address (MSB=1 as mark of address - 4 bits LSB)
- UART_CR4.ADD: own address
- only first byte after idle considered as possibly containing address mark? not clear.

jobs

MAYHALT - semaphore, must be incremented on start of each no-halt process e.g. UART TX syssleep func:

 check for mayhalt
 if zero halt
 if not wfi
 loop if no jobs else get toppest by pri and start

sysjobs:

 populated with int handlers, address of jobs to run (with associated data ptr)

?sysqueues: ? if smth is put on it, associated job is created by system